Fix creating target paths in file_util_posix CopyDirectory.

base/file_util_posix.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/file_util.h"
 
 #include <dirent.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <fnmatch.h>
@@ skipping 325 matching lines @@
     // If the destination already exists and is a directory, then the
     // top level of source needs to be copied.
     from_path_base = from_path.DirName();
   }
 
   // The Windows version of this function assumes that non-recursive calls
   // will always have a directory for from_path.
   DCHECK(recursive || S_ISDIR(info.stat.st_mode));
 
   while (success && !current.empty()) {
-    // current is the source path, including from_path, so paste
-    // the suffix after from_path onto to_path to create the target_path.
-    std::string suffix(&current.value().c_str()[from_path_base.value().size()]);
-    // Strip the leading '/' (if any).
-    if (!suffix.empty()) {
-      DCHECK_EQ('/', suffix[0]);
-      suffix.erase(0, 1);
+    // current is the source path, including from_path, so append
+    // the suffix after from_path to to_path to create the target_path.
+    FilePath target_path(to_path);
+    if (from_path_base != current) {
+      if (!from_path_base.AppendRelativePath(current, &target_path)) {
+        success = false;
+        break;
+      }
     }
-    const FilePath target_path = to_path.Append(suffix);
 
     if (S_ISDIR(info.stat.st_mode)) {
       if (mkdir(target_path.value().c_str(), info.stat.st_mode & 01777) != 0 &&
           errno != EEXIST) {
         DLOG(ERROR) << "CopyDirectory() couldn't create directory: "
                     << target_path.value() << " errno = " << errno;
         success = false;
       }
     } else if (S_ISREG(info.stat.st_mode)) {
       if (!CopyFile(current, target_path)) {
@@ skipping 759 matching lines @@
 
     allowed_group_ids.insert(group_record->gr_gid);
   }
 
   return VerifyPathControlledByUser(
       kFileSystemRoot, path, kRootUid, allowed_group_ids);
 }
 #endif  // defined(OS_MACOSX) && !defined(OS_IOS)
 
 }  // namespace file_util